IMAGINE A TOY boat that could fit in the palm of your hand. In the middle of the ship, add a spool of sewing thread lying on the side. Increase that by about a thousand and the result is 150 yards long Nexans Aurora. The wire in question is made up of miles of high voltage power line ready to be deployed from the stern of the ship across the seabed. Each cable, weighing 150 kg per meter and thick as a tree trunk, is a woven mixture of aluminum, steel, lead and insulating material. The single section loaded in a coil nearly 30 meters in diameter is as heavy as the Eiffel Tower.

The ways in which electricity is both consumed (more, especially by cars) and produced (also more, increasingly via renewable sources, see Figure 1) are changing. Balancing energy supply and demand is never easy, as the chaos in European gas markets has shown. It is all the more complex for electricity, more delicate to store than not only gas, but also coal, diesel or wood chips. Renewable energies add more wrinkles: the wind blows at random; the sun can be obscured by clouds or at night. As a result, most of the energy produced must be consumed immediately, and primarily where it is produced.

The idea of ​​separating consumption from production over time – using giant batteries or other means of storage – has received a lot of attention from entrepreneurs, politicians and investors. But it is currently impractical on a large scale. Thus, the idea of ​​separating the two in space is gaining ground. It requires a behind-the-scenes wiring upgrade that carries power from its place of manufacture to its place of use. The task may involve connecting an offshore wind farm to the grid. Connections to national grids are also needed, often within blocks where most of today’s electricity trade takes place, such as the EU.

Meeting the ups and downs of electricity demand is complicated but well understood. UK grid managers have long known how to turn on power plants as the soap operas end and tea-hungry viewers turn on their kettles. Connecting electricity grids with different production and consumption patterns is equivalent, matching supply and demand by transferring electricity remotely.

Take Denmark. He has installed enough wind turbines that no other source of electrical power is needed when it blows. But he needs a plan B, given the inconstancy of the wind. Without batteries, it could keep old fossil fuel plants open and use them intermittently. A more elegant solution is a cable to Norway, which has significant hydroelectric potential. When the wind blows, both places can use Danish wind power, keeping Norwegian water in reservoirs. On calm days, the Norwegian lakes drain a little faster to rescue Denmark.

Further connections from Denmark to the Netherlands, Sweden, Germany and Great Britain (scheduled for 2023) offer even more options. Add enough links in enough places and electricity becomes a tradable commodity. For a local grid operator, reducing carbon emissions becomes a matter of buying and selling the right contract rather than building a solar or wind farm in the wrong place.

This perspective explains why interconnections are multiplying. Europe is the new frontier for cable laying. Electrification, in particular via renewable energies, is a key element of its ambitions to reach “net zero†by 2050. National networks have been constrained by EU rules to be integrated into a single network, often backed by public funds. The continent’s rugged coastline is ideal for wind power and for deploying power cables at sea, out of sight of anyone who might object.

The changing dynamics of energy production play a role. Germany, for example, was once a major exporter of electricity, but is becoming an importer as it completes the shutdown of its nuclear power plants and phase out coal. The green push also means electricity is being produced in all the wrong places. In Italy, power stations have been built near industrial areas, mainly in the north of the country. Now the wind is blowing and the sun is mainly shining in the less developed south. “The shift to renewables means we need more rebalancing, more transition,†says Stefano Antonio Donnarumma de Terna, an Italian transmission line manager.

As a result, the manufacture and deployment of electric cables is one of the few industrial sectors dominated by European companies. Besides French Nexans, Prysmian is Italian and NKT is Danish. They have around 80% market share outside of China, where demand is largely met locally. Beyond the simple manufacture of woven metal wires (among other products), they also lay them, commission and operate ships like the Nexans Dawn, a 170 million euro boat built the coast from an existing Nexans factory in Halden, Norway.

Progress in laying submarine cables has opened up the prospect of new, unprecedented interconnections. While previous generations of ships were at risk of tipping over if they sent cables well below 1,200 meters, the Nexans Aurora and a flotilla of similar vessels from its rivals can lay the cables at depths of 3,000 meters. (An accompanying robot can dig a trench in shallower water, to better protect itself from stray anchors and fishing nets.) This opens up the Mediterranean. This week on Nexans Aurora was preparing to deploy its first cable, connecting the island of Crete to the Greek mainland.

Longer cables mean less legs of around 100 km that have to be sewn together. As a result, the viability of much longer interconnections is discussed. A 720 km link between Norway and Great Britain began operating this month. Many are in various stages of planning, for example connecting Greece and Israel, or Ireland and France. Others are more speculative, such as a 3,800 km cable connecting the sunny solar fields of Morocco to Great Britain. Another consortium wants to link Australia, Indonesia and Singapore, a 4,200 km project.

According to Christopher Guérin, head of Nexans, 72,000 km of cables of this type will be laid by 2030, seven times the current stock. This is in addition to the wiring needed to upgrade outdated connections on land, many of which have passed their expiration dates. An electricity crisis in Texas earlier this year also helped unlock stimulus funds for grid upgrades in America.

A more immediate opportunity is to connect wind farms to onshore power grids. Cable vendors are encouraged by the fact that more and more such facilities are being developed far offshore. The possibility of floating wind farms, which could be even further away, will add to their order books. The International Energy Agency, an energy club of rich countries, estimates that 80 gigawatts of offshore wind farms will need to be installed each year by 2030 to meet decarbonization targets. Each gigawatt of offshore capacity requires around 250 million euros of cable, including installation, says Max Yates of Credit Suisse. The cable costs about as much as the foundation, behind just the turbine itself.

The urgency of this global rewiring effort is almost imperceptible from the deck of the Nexans Aurora. The spools release their thread at a leisurely pace: 10 to 12 km per day is considered neat work. But the future energy highways are finally becoming a reality. Stable as she goes. â– 

This article appeared in the Business section of the print edition under the headline “An Underwater Change”